Propane (c3 h8 (g), hf = –103.8 kj/mol) reacts with oxygen to produce carbon dioxide (co2 , hf = –393.5 kj/mol ) and water (h2 o, hf = –241.82 kj/mol) according to the equation below.

i'm assuming that the correct answer is indeed the first one/ "a"..

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.

i just calculated it all out, and not including weekends, and all the different days off. as of this school year (2018-2019) students are spending 2198 hours in school this year